Equatorial Sector to First Point of Cancer

An instrument employed for ascertaining the difference in the declination and right ascension of two heavenly bodies.

A telescope mounted in such a manner that the observer is enabled to follow the stars in their movement across the heavens.

A rhumb line; a line cutting the meridians at a constant angle.

The celestial equator.

The meridian passing through the equinoctial points.

Storms occurring about the time the sun crosses the equator-about March 21 and September 20.

The two opposite points in which the ecliptic and equinoctial intersect each other. The points where the sun crosses the equator, which occurs about March 21 and September 22. When this occurs the days and nights are of equal length throughout the world. About 4,000 years ago the position of the Vernal Equinox coincided with the constellation Aries, but owing to the precession of the equinoxes this point is now in the constellation Pisces. (See First Point of Aries, Precession of the Equinoxes, Tropic of Cancer, Tropic of Capricorn.)

It being of great importance to determine the time of high water for various ports, a standard tide is fixed upon, which is indicated by a relative position of the sun and moon, and from which the time of every tide may be deduced. This is known as the establishment of the port.

Winds that blow at stated times of the year.

The inventor of the mercurial thermometer (a temperature measurer) was Gabriel Daniel Fahrenheit, who first made the instrument known in 1714.

To take departure. (See Departure.)

Six feet.

The circular space in a telescope in which, when the instrument is in focus, objects are visible.

Same as prime meridian. A great circle selected as the starting point of longitude; the meridian which passes over the national observatory of a country is generally counted the first or prime meridian. The French adopt the meridian of Paris, the Spaniards that of San Fernando, the English that of Greenwich, the Russians that of St. Petersburg, the Americans that of Washington, etc.

The vernal equinoctial point; the first of the twelve signs which the sun enters at the vernal equinox. The commencement of this sign is called the first point of Aries, and it is the origin from which the right ascensions of heavenly bodies are reckoned upon the equator, and their longitudes upon the ecliptic.

The summer solstitial point, which the sun enters about the 21st of June.